Fossils

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Evolution The Science behind the theory

• Geological time
• Fossils
• Darwin Natural Selection
• Species changing over time
• Anatomical Embryological evidence
• Speciation

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Summary of Evolution of Life
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How do we know about the past?
Fossils
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What is a fossil?

• A fossil is an impression, cast,
• original material or track of any animal or
  plant that is preserved in rock after the
  original organic material is transformed or
  removed.

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A fossil may be

• an original skeleton or shell
• a mold or cast
• traces such as footprints or worm tubes

Material that has replaced the once living thing
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Types of Fossils

• Body fossils
• actual parts of an organism
• bones, shells, leaf imprints

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Types of Fossils

• Trace fossils
• evidence of life having been there tracks,
  burrows, casts

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Trace Fossils

• Mold reproduction of the inside or outside
  surface of a living thing
• Cast duplicate of the original organism
  usually formed by replacement of inside of living
  thing

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Trace Fossils

• Burrows or borings
• Spaces dug out by living things preserved as
  is or filled in

Tracks impressions of passage of living things
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Trace Fossils
Imprint Thin objects such as a leaf that
falls onto sediment leaves an imprint then the
sediment hardens into rock
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Petrified Fossils
Minerals penetrate replace the hard parts
of an organism producing a copy of them
Amber Ice
An entire organism was quickly trapped in ice or
tree sap that hardens into amber
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Where are fossils found?
Sedimentary Rock
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Why sedimentary rock?
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What conditions promote fossilization?

• Hard body parts such as skeletal bones or
  exoskeletons

Rapid burial and/or lack of Oxygen
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Unaltered - insects or plant parts trapped in
amber or ice original unaltered material from
the living organism
Replacement the hard parts of an organism
dissolve and are replaced by other minerals
Petrification rock-like minerals seep in slowly
and replace the original organic tissues
Authigenic- molds or casts of organisms tissue
material is decomposed or of markings left behind
by an orgasnism
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• Putting it all together

Examples of Fossils . . .
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Sporadoceras
Nautilus
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Orthoceras
Squid
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Trilobites
Lobster
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Fossil Fish
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Dinosaur Bones